Phytophthora and crown rot (PRR), caused by Phytophtora capsici (Leon), is one of the most damaging fungal diseases affecting pepper (Capsicum). Cultural control measures and fungicide usage are only partly successful at controlling this disease. We wish to tag loci which confer resistance to genotypes of pepper. We also will investigate possible orthology between pepper loci and loci conferring resistance to P. infestans in tomato and potato. Specific strategies to achieve these goals are (1) Closely tagging (within 1 cM) the major PRR resistance gene from C. annuum CM334 with flanking molecular markers (RAPDs, AFLPs, RFLPs), (2) Creating a high-resolution map of that region using a population of 350 F2 plants, (3) Mapping locations of the resistance QTLs in the PI201234 X Psp-11 cross using RAPDs, AFLPs, and RFLPs, (4) Comparing locations of Phytophtora resistance genes in both pepper crosses to each other and to those in potato and tomato, as well as to other disease resistance gene locations in pepper (are there orthologous disease resistance gene loci?), (5) converting the molecular markers that are most closely linked to the PRR resistance genes to SCARs (sequence- characterized amplified regions) for ease of future marker-assisted selection )MAS), and (6) Testing P. capsici isolates with molecular markers to assess variability within the species and to search for virulence markers. Tagging of PRR resistance genes in pepper will provide tools to enhance the transfer of resistance to other genotypes, and will decrease grower's reliance on chemical control measures. Information gained about the relationships among disease resistance loci may provide for future strategies to enhance resistance to multiple plant pathogens and may illuminated the fungal pathogen-host organism interaction, which may have broad applicability to question of human fungal pathogenesis.